Transcript ANDREWS’ DISEASES OF THE SKIN

ANDREWS’
DISEASES OF THE SKIN
Tenth Edition
Chapter 1
The Skin: Basic Structure and Function
Elaine Miller, D.O.,
July 18, 2006
Basic Structure – 3 Layers
1. Epidermis
2. Dermis
3. Subcutaneous Fat
 Considerable regional variation in their
relative thickness
Normal Skin: Trunk vs. Palm
Epidermis
• The adult epidermis is composed of three
basic cell types:
1. Keratinocytes
2. Melanocytes
3. Langerhans cells
• Adnexal structures: follicles and eccrine
glands originate during the third month of
fetal life
Epidermis: 1. Keratinocyte
• Principal cell of the
epidermis (80%)
• Ectodermal origin
• Produces keratin
• Zones:
– Basal layer
– Stratum Spinosum
Malphighian layer/prickle
layer
– Granular layer
– Stratum corneum
Epidermis: 1. Keratinocyte
• Mitotically active
• Changes as it moves
upward through the
epidermis
• Basal cell layer is
generally one cell
thick wherever its
location
Epidermis: 2. Melanocyte
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Produce Pigment
Derived from Neural Crest
Found in the fetal epidermis in the 8th week
Usually in the basal layer, approximately 1
for every 10 basal keratinocytes
• Numbers are same regardless of race or
color
Epidermis: 2. Melanocyte
• Melanocytes are dendritic cells which are in
contact with a number of keratinocytes thus
forming the epidermal melanin unit
• Number and size of MELANOSOMES determines
skin color!!!
• Melanocytes in dark skin synthesize larger
melanosomes than those produced in light skin
• Larger melanosomes are also produced with
chronic sun exposure
Epidermis: 2. Melanocyte
• Melanocyte
Abnormalities:
– Vitiligo – destruction
of melanocytes
– Albinism – melanocyte
number is normal, but
they are unable to
synthesize fully
pigmented
melanosomes
Epidermis: 3. Langerhans Cell
• Scattered among keratinocytes in the
stratum spinosum with no desmosome
connections
• 3-5% of cells here
• Folded nucleus
• Birbeck granules
• Originate in bone marrow
• Functionally monocyte-macrophage lineage
Langerhans Cells have Birbeck
Granules
Epidermis: Merkel Cell
• Found in the basal
layer of the palms &
soles, oral and genital
mucosa, nail bed and
follicular infundibula
• Located directly above
the Basement
Membrane
• Act as slow adapting
touch receptors
Epidermal Appendages: The Adnexa
1. Eccrine Sweat Units
2. Apocrine Units
3. Pilosebaceous Units
 Originate as down growths from the epidermis
 Adnexal structures serve specific functions
 All can functions as reserve epidermis, occurring
principally by virtue of migration
Adenexa: 1. Eccrine Sweat Unit
• Found at virtually all
skin sites
• Most abundant on the
palms, soles, forehead
and axilla
• Cholinergic
Innervation
• Regulates temperature
by excreting sweat
Adenexa: 2. Apocrine Unit
• Develops as an outgrowth
of the infundibulum or
upper portion of the hair
follicle
• Located in the axilla,
areola, ano-genital area,
external auditory canal,
and eyelids
• Serves no known function
in humans
• Secretion is mediated by
adrenergic innervation
Adenexa: 3. Pilosebaceous Unit
• Pilosebaceous Unit:
– 2-4 hairs
– associated sebaceous
gland
– arrector pili muscle
– collagen
• Hair is composed of
keratin
• Three types of hair:
lanugo (fine), vellus,
and terminal (coarse)
Adenexa: 3. Pilosebaceous Unit
Hair Follicles
• Infundibulum: from the uppermost portion
to the entrance of the sebaceous duct
• Isthmus: from the sebaceous duct to the
insertion of the erector pili muscle
• Inferior portion: the lowest part of the
follicle and the hair bulb which cycles
through involution and regeneration
• Hair shaft and the inner and outer root
sheath develop from mitotically active
undifferentiated cells of the matrix
Hair Follicle
Phases of Scalp Hair Growth
1. Anagen (growth)
~ 3-5 years (85-90% of hair)
 Pigmented bulb
2. Catagen (involution)
~ 2 weeks (1%)
 Apoptotic cells in outer
root sheath
3. Telogen (resting)
~ 3-5 months
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Lose 50-150 per day
Club shaped hairs with
non-pigmented bulb and
shaggy lower border
Adenexa: 3. Pilosebaceous Unit
Hair Follicles
• The cross-sectional shape of the hair
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depends on the arrangement of cells in the
bulb
Hair color depends on the distribution of
melanosomes within hair bulb
Black person’s hair = Big melanosomes
White person’s hair = smaller melanosomes
Red hair = Round melanosomes
Gray hair = decreased melanocytes
Adenexa: 3. Pilosebaceous Unit
Sebaceous Glands
• Formed embryologically as an outgrowth from the upper
portion of the hair follicle
• At all skin sites except palms and soles
• Dense on the face and scalp
• Always associated with hair follicles except at:
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Eyelids (meibomian glands)
Buccal mucosa
Vermilion border of the lip (Fordyce spots)
Prepuce (Tyson glands)
Female areolas (Montgomery tubercles)
• Holocrine Secretion under hormonal control (androgens)
Nails
• Matrix keratinization
leads to the formation
of the nail plate
• Keratin types found in
the nail are a mixture
of epidermal and hair
types
• Fingernails grow an
average of 0.1
mm/day, slower for
toenails
Nails
• Abnormalities may serve as important clues to
cutaneous and systemic disease
• Example:
A 72-year-old woman with diabetes, hypertension, and
peripheral vascular disease was hospitalized with chest
tightness and acute shortness of breath. She reported a
four-month history of worsening dyspnea on exertion,
orthopnea, and a progressive whitening of her fingernails
A 72-year-old woman with diabetes mellitus, hypertension, and peripheral vascular disease was
hospitalized with chest tightness and acute shortness of breath
Antonarakis E. N Engl J Med 2006;355:e2
Acquired Leukonychia Totalis
• Acquired leukonychia totalis has been associated
with several systemic diseases, including hepatic
cirrhosis, chronic renal failure, congestive heart
failure, diabetes mellitus, chronic
hypoalbuminemia, and Hodgkin's lymphoma.
• The patient underwent coronary angioplasty with
stent insertion in the affected artery. At follow-up
six months later, the appearance of her nails had
returned to normal.
The Dermoepidermal Junction
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Formed by the Basement Membrane Zone (BMZ)
Composed of four components
1.
Plasma membranes of the basal cells
with hemidesmosomes
2.
3.
Lamina lucida
Lamina densa (Basal lamina)
mostly Type IV collagen
4.
Fibrous components associated
with the basal lamina: anchoring fibrils
(Type VII Collagen), dermal micro-fibrils, and collagen
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BMZ is a semi-permeable filter
Serves as structural support for the epidermis
The Dermis
• The constituents of the dermis are of
mesodermal origin, with the exception of
nerves
• The principal component of the dermis is
collagen, a family of fibrous proteins having
at least 15 genetically distinct types in
human skin
• Represents 70% of the dry weight of the
skin
The Dermis
• Fibroblast synthesize procollagen molecules that
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are secreted by the cells and assembled into
collagen fibrils
Collagen is rich in the amino acids
hydroxyproline, hydroxylysine and glycine
Type I collagen is the major component of the
dermis – it has a uniform structure
Collagen fibers are loosely arranged in the upper
dermis (papillary dermis)
Tightly bundled in a fascicle-like pattern in the
lower dermis (reticular dermis)
The Dermis
• Type VII collagen is the major structural
component of anchoring fibrils and is
produced predominantly by keratinocytes
• Fibroblast also synthesize elastic fibers and
ground substance of the dermis
Desmosine and isodesmosine are amino acids
that are unique to elastic fibers
Elastic fibers differ structurally and chemically
from collagen
Collagen
• It is the major stress-resistant material of the
skin
– Elastic fibers contribute very little to resisting
deformation and tearing of the skin, but have a
role in maintaining elasticity
• Connective tissue disease is a term
generally used to refer to a heterogenous
group of autoimmune diseases that affect
collagen and/or dermal mucin
Defects in Connective Tissue
• Defects in Collagen synthesis
Ehlers-Danlos syndrome
X-linked cutis laxa
Osteogenesis imperfecta
• Defects in elastic tissue
Marfan syndrome
Pseudoxanthoma elasticum
Vasculature of the Skin
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Consists of two main intercommunicating plexuses
1. Subpapillary plexus/upper horizontal network
 At the junction of the papillary and reticular
dermis
 Perfuses the dermal papilla
2. Lower horizontal plexus
 At the dermal-subcutaneous interface
 Larger blood vessels
Adnexal structures of the dermis are well vascularized
Muscles of the Skin
• Smooth muscle:
– Occurs in the skin as arrectores pilorum
– Comprises the muscularis of dermal and subcutaneous
blood vessels
– Specialized aggregates are called Glomus bodies
ocuring between arterioles and venules
• Glomus bodies are prominent on the digits and at the lateral
margins of the palms and soles
• Striated (voluntary) muscle:
– In the neck skin as the platysma muscle
– In the facial skin as the muscles of facial expression
Nerves of the Skin
• Neurovascular bundles - > VAN
• Meissner corpuscles
– Mediate touch and pressure
– Located in the dermal papillae especially in the hands and feet
• Vater-Pacini corpuscles
– Mediate pressure
– Located in the deeper dermis of weight-bearing surfaces and the
genitalia
• Temperature, pain and itch sensations are transmitted by
unmyelinated nerve fibers which terminate in the papillary
dermis and around hair follicles
Mast cells of the dermis
Mast Cells of the Dermis
• An important cellular constituent of the dermis
• Resemble fried eggs in histologic sections
• Contain up to 1000 granules which in turn contain
heparin, histamine, and various other factors
• Surface contains up to to 500,000 glycoprotein
receptor sites for IgE
• Respond to environmental changes, for example, in
dry environments the number of mast cells increases
as does the histamine content
Subcutaneous Tissue (Fat)
Subcutaneous Tissue (Fat)
• Beneath the dermis lies the panniculus, lobules of
fat cells or lipocytes separated by fibrous septa
composed of collagen and large blood vessels.
• Collagen in the septa is continuous with the
collagen in the dermis
• It provides buoyancy, stores energy, and is an
important site of hormone conversion
• Inflammatory conditions that affect the panniculus
can be differentiated from each other based on
whether it mainly affects the septa or the fat
lobules themselves
CUTANEOUS SIGNS AND
DIAGNOSIS
Chapter 2
CUTANEOUS SIGNS AND DIAGNOSIS
• The same disease may show variations
under different conditions and in different
people
• The appearance of lesions may have been
modified by previous treatments or
obscured by extraneous influences
(scratching, secondary infection)
• Subjective symptoms may be the only
evidence of disease (pruritis, pain)
CUTANEOUS SIGNS AND DIAGNOSIS
• Although history is important; however, in
Dermatology, the diagnosis is most
frequently made based on the objective
physical characteristics and location or
distribution of one or more lesions that can
be seen or felt
• Careful physical exam is paramount
PRIMARY LESIONS
Macules and Patches
Papules, Plaques and Pustules
Nodules and Tumors
Vesicles and Bullae
Wheals (Hives)
Primary Lesions: 1. Macules
• Without elevation or
depression
• Less than 1 cm in size
• Circular oval or irregular
• Circumscribed changes in
the skin color
Primary Lesions: 2. Patches
• A large macule
• 1 cm or greater in
diameter
• Nevus flammeus or
vitiligo
Primary Lesions: 3. Papules
• Circumscribed, solid
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elevations, varying in size
from pinhead to 1 cm
May be rounded, flattopped, conical, or
umbilacated
May be soft or firm
Called papulosquamous
when capped by scales
May be discrete,
irregularly distributed or
grouped
Primary Lesions: 4. Plaques
• A broad papule or a
confluence of
papules
• 1 cm or more in
diameter
• Generally flat
but may be
depressed
Primary Lesions: 5. Pustules
• Small elevations of the
skin containing
purulent material
• Similar to vesicles and
have an inflammatory
areola
• White, yellow or red
• May start as pustules
or develop from
papules or vesicles
Primary Lesions: 6. Nodules
• Morphologically
similar to papules
• More than 1 cm in
diameter
• Most frequently are
centered on the dermis
or the subcutaneous
fat
Primary Lesions: 8. Wheals or Hives
• Evanescent, edematous,
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plateau-like elevations of
various sizes
Usually oval or arcuate
contours
Pink to red
Surrounded by a pink
areola
May be discrete or
coalesce
Primary Lesions: 9. Vesicles
• Circumscribed, fluid•
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containing, epidermal
elevations 1-10 mm
Apex may be rounded,
acuminate, or umbilacated
Discrete, irregularly
scattered, grouped or
linear
May develop into bullae
or pustules
Unilocular or multilocular
Primary Lesions: 10. Bullae
• Rounded or irregularly
shaped blisters
containing serous or
seropurulent fluid
• Greater than 1 cm
• Typically unilocular
• May be located in the
epidermis or
subepidermal
More About Bullae
• Nikolsky’s sign, diagnostic maneuver of
putting lateral pressure on unblistered skin
in a bullous eruption with shearing of the
epithelium
• Absoe-Hansen’s sign, extension of a blister
to adjacent unblistered skin when pressure
is put on top of the blister
• Cellular contents of the bullae may be
useful in confirming the diagnosis
SECONDARY LESIONS
Scales
Crusts
Excoriations and Abrasions
Erosions, Ulcers, Fissures
Scars
Secondary Lesions: 1. Scales
• Dry or greasy keratin
laminated in masses
• Due to rapid formation
of epidermal cells and
pathologic exfoliation
• Vary in size & color
• May have a silvery
sheen from trapping of
air between layers
Secondary Lesions: 2. Crusts
• Collections of dry
serum, pus, or blood,
usually mixed with
epithelial and/or
bacterial debris
• Vary in size, shape
thickness and color
• When they become
detached the base may
be dry or moist
Secondary Lesions: 3. Excoriations
• An excoriation is a
punctate or linear
abrasion produced by
mechanical means,
usually involving only
the epidermis, but not
uncommonly reaching
the papillary layer of
the dermis
• Caused by scratching
Secondary Lesions: 4. Abrasions
• If the damage is a
result of mechanical
trauma or constant
friction – abrasion
• Frequently has an
inflammatory areola
• May provide access
for pyogenic
organisms
Secondary Lesions: 5. Fissures
• Linear cleft through
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the epidermis or even
into the dermis
Single or multiple
Microscopic to several
centimeters in length
Sharply defined
May be dry, moist,
red, straight, curved,
irregular, or branching
Secondary Lesion: 5. Erosions
• Loss of all or portions
of the epidermis alone
• May not become
crusted
• Heals without a scar
Secondary Lesion: 6. Ulcers
• Rounded or irregularly
shaped excavations
that result from
complete loss of the
epidermis plus some
of the portions of the
dermis
• Various sizes, shallow
or deep
• Heal with scarring
Secondary Lesions: 6. Scars
• Composed of new
connective tissue that
replaced lost substance
in the dermis or deeper
parts as a result of
injury or disease, as
part of the normal
reparative process
• Characteristic of
certain inflammatory
processes
Secondary Lesions: 6. Scars
• Pink initially later
becoming white and
glistening
• Scars may be thin and
atrophic or keloids
• May be smooth or
rough, pliable or firm
Diagnostic Details of Lesions
Distribution of Lesions
• Few or numerous
• Local or diffuse
• Discrete or Coalesced
to patches of peculiar
configuration
• Dermatomes – Zoster
• Blaschko’s lines –
epidermal nevi
Evolution of Lesions
• Some stay the same
(nevi)
• Some start small and
get bigger
• Some have
characteristic changes
with time (varicella)
Involution
• Lesions may disappear
completely
• May leave
characteristic residual
pigmentation or
scarring
• Keratotic papule of
pleva
Grouping
• Characteristic of DH,
herpes simplex, herpes
zoster, and late
syphilitic eruptions
• Linear (breakfastlunch-and-dinner), flea
and other arthropod
bites
Configuration
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Annular
Linear
Serpiginous
Arcuate
Polycyclic
Guttate
Nummular
Unusual configurations
may be exogenously
induced
Color
• The Tyndall effect modifies the color of the
skin and the color of the lesions by the
selective scattering of light waves of
different wave-lengths. The blue nevus and
mongolian spots are examples of this light
dispersion effect
• Not advisable to place too much reliance on
color
Color
• Patches lighter in color
than normal skin may be
completely depigmented
or have lost only part of
their pigment
• Hyperpigmentation may
be a result of epidermal or
dermal causes
• Hyperpigmentation
following inflammation is
most commonly the result
of dermal melanin
deposition
Consistency – Palpate the Lesion
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Blanchable
Fluctuant
Doughy
Hot or cold
Firm or calcified
The End